The present disclosure relates to a projection-type display apparatus including a laser light source.
In recent years, there has been an increasing demand for miniaturization of projection-type display apparatuses. The projection-type display apparatuses can be miniaturized by using semiconductor laser light sources (hereinafter, referred to as just a laser light source) instead of xenon lamps and ultrahigh pressure mercury lamps, which are conventionally used.
However, the laser light sources have low light emission efficiency and high coherence to be used as the light sources of the projection-type display apparatuses. Especially, the high coherence thereof in particular, produces an interference pattern called speckle, and worsens the quality of projected images.
In order to solve this problem, various proposals have been made. Japanese Patent Laid-open Publication No. 2009-169012 (Patent Literature 1) describes that continuous rotation of a prism or a mirror reduces speckle. Japanese Patent Laid-open Publication No. 2008-256824 (Patent Literature 2) describes that translating a reflection plate in a reciprocating manner reduces speckle.